An accurate understanding of the estrous or heat cycle in a cow constitutes valuable information. Using this information, an accurate ovulation time period can be identified during which the cow is typically artificially inseminated. In the case of a dairy cow, a successful insemination means that desired milk production from the cow is achieved. On the other hand, a failure to achieve pregnancy in the cow usually means lost milk production for a period of time until after one or more additional heat cycles. A longer than necessary calving interval where the cow is not pregnant when she should be results in lost sales of milk.. For a herd of cows where estrus is not accurately detected, such a failure can annually cost the dairyman thousands of dollars due to milk production losses.
The importance of estrus detection in cows has been recognized in a number of issued U.S. patents. Generally, these patents describe in detail problems faced in making decisions concerning when to artificially inseminate a cow. In U.S. Pat. Nos. 4,846,106 and 4,635,587, issued Jul. 11, 1989 and Jan. 13, 1987, respectively, and entitled "Method and Apparatus for Detecting Standing Heat in Cattle," the economic significance of accurate heat detection is described. Relatedly, the relevance of cow mounts and the time periods germane to artificial insemination including the relevance of the heat cycle are also discussed. These patents disclose a module attached to the cow that displays the cow mount duration directly on the cow and also provides a warning signal to inform the cow owner that a mount has occurred.
A number of other patents disclose heat detection apparatuses. In U.S. Pat. No. 4,411,274 to Wright, issued Oct. 25, 1983 and entitled "Apparatus and Method for Monitoring the Oestrus Cycle in Female Animals" a pad is disclosed for attachment to the cow. The pad houses a transmitter module for transmitting data relating to the frequency of cow mounts. The transmitter module includes control circuitry responsive to a pressure switch that is activated when the cow is mounted. The control circuitry includes time delay circuitry for preventing signal transmission until a predetermined time lapse occurs from the time the switch is initially activated, which is independent of the length of switch activation. This transmitter module also includes an encoder and a small rf transmitter. The transmitted signal is sent to a receiving unit that includes a decoder. Printed information is provided to identify the cow that was mounted and the actual time that the mount occurred, but not the duration of the mount. U.S. Pat. No. 4,247,758 to Rodrian issued Jan. 27, 1981 and entitled "Animal Identification and Estrus Detection System" describes a transponder carried by a cow that is activatable to transmit data relating to the number of body movements of the animal and an identification number. The transponder is interrogated by a receiver before transmitting such data. U.S. Pat. No. 4,895,165 to Blair issued Jan. 23, 1990, and entitled "Electronic Estrus Detector" describes an algorithm for determining the onset of estrus that relies on the sum of all estrus mounts and the sum of all estrus mount times. This patent also indicates that the pouch attached to the cow may be made from nylon, canvas, fabric or other similar materials or combinations of such materials. U.S. Pat. No. 4,503,808 to McAlister issued Mar. 12, 1985 and entitled "Animal Herd Management System" is directed to the detection of standing heat and utilizes a transmitter implanted in the body of the animal. An identification signal uniquely identifying the animal and time of day signals are transmitted. U.S. Pat. No. 3,844,273 to Polson issued Oct. 29, 1974, and entitled "Method and Apparatus for Animal Heat Detection and Recording" relates to an electronic heat detection system that includes a transmitter unit attached to the cow and which also includes a timer that monitors the time from the beginning of a cow mount to the isolation of the cow. The transmitter unit sends transmitted data to a remote location for analysis. U.S. Pat. No. 5,111,799 to Senger et al. issued May 12, 1992 and entitled "Estrous Detection Systems" relates to a transmitting device implanted under the hide of the animal. This device includes a force responsive switch in which two contacts are forced together during a cow mount. U.S. Pat. No. 4,618,861 to Gettens et al. issued Oct. 21, 1986 and entitled "Passive Activity Monitor for Livestock" discloses a system that monitors an animal's activity by means of a transponder/activity monitor that is carried around the animal's neck and the motion thereof is used in determining the onset of estrus.
Despite the numerous proposals or disclosures directed to heat detection in cows, it appears that none of these have achieved the desired success in the market place. Consequently, a practical solution to the problem of heat detection would be significantly worthwhile to the cow owner. A practical heat detection system should be easy to implement and utilize, as well as providing for enhanced detection of estrus, while the savings realized by the herd owner is outweighed by the cost of such a system.